Friday, June 18, 2010

The Blood Factory

Learning that your bones are made of living tissue may surprise you, but your bones have even more going on. This time, however, the party’s on the inside.

To understand what takes place, you need to realize that bones aren’t solid all the way through. Instead, your bones have a hard outer layer and a honeycombed inner layer that’s laced with tiny holes. This combination gives bones an interesting characteristic—they’re both impressively strong and surprisingly light. In fact, for their weight, bones are one of the strongest materials on earth.

Furthermore, many bones have a hollow cavity packed with jelly-like bone marrow. Bone marrow comes in two flavors: yellow marrow, which simply stores fat, and red marrow, which creates new blood cells. Thanks to the red marrow, your bones are nonstop assembly lines, churning out more than 100 billion blood cells every day—important work indeed. In fact, a bone somewhere in your body created every blood cell that’s circulating in your body right now.

Clearly your bones deserve more respect than they usually get. So the next time you see a skull and crossbones slapped on a bottle of lethal toiletbowl cleaner, take a moment to reflect on your bones and their life-giving role as your body’s bottomless blood bank.

Yellow marrow is found in the middle of long bones, like those in your legs. Red marrow is found primarily in flatter bones, like your hip bones, breast bone, skull, and shoulder blades.

Bone marrow doubles as a supremely nutritious food delicacy (at least when it’s from some other creature’s bones). Packed with protein and unsaturated fat, it’s a key ingredient in Vietnamese pho soup and the highlight of Italian osso bucco (braised veal shanks). Some anthropologists even believe that marrow was a staple in the diet of our distant ancestors. The theory is that these early humans were inept hunters who rarely caught a good meal—so they spent most of their mealtime cracking open the bones that more capable predators left behind.

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In its broadest sense, science (from the Latin scientia, meaning "knowledge") refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research.

Fields of science are commonly classified along two major lines: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.